The present invention broadly relates to conveyor belt scrapers or cleaners. More particularly, our invention relates to mechanical biasing systems for conveyor belt cleaners.
As is well known in the art, materials handled by conveyor belts often tend to stick to the belt surface. Numerous conveyor belt cleaner systems have been proposed for cleaning purposes. Systems that hold a series of teeth or blades against a conveyor belt surface to scrape off material adhering to the belt have been present in the industry for years. Such systems have removable blades and adjustment systems for varying the position of the blades relative to the conveyor belt. Such a system is disclosed, for example, in U.S. Pat. No. 4,953,689.
Cleaning blades or scraping structures must normally be mechanically biased against the belt surface to be cleaned for maximum efficiency. Such a system is disclosed in Swinderman U.S. Pat. No. 4,944,386. This patent discloses a weighted, generally V-shaped blade that is tethered to a frame encompassing a conveyor belt. The downward pressure of the scraper is increased by the addition of ballast to a housing disposed on the scraper. Lenbek, U.S. Pat. No. 4,586,600, relates to a torsioning arrangement for a belt cleaner which employs a camming feature to hold the scrapers in the cleaning position against the belt. Stahura U.S. Pat. No. 4,098,394 discloses a mounting support arrangement for a conveyor belt cleaner which employs a ratchet system to keep the scrapers biased against the belt and a locking dog to secure the shaft containing the blades against counter rotation.
Swinderman U.S. Pat. No. 4,925,434 discloses a torsional tension device for imparting torsional bias to the shaft containing the cleaning blades while simultaneously providing a shock absorbing mechanism. This is accomplished by a series of hubs and a torsion coupling of elastomeric material connecting the two hubs together. Bushings of elastomeric material provide the shock absorbing feature of the Swinderman patent, while set screws lock the shaft in a position imparting tension through the blades against the belt.
Other devices for biasing blades against a conveyor belt are disclosed in Gordon, U.S. Pat. Nos. 4,202,437; 4,231,471 and 4,533,036. The first of these patents discloses a conveyor belt scraper assembly having three sets of blades disposed on a rotating housing. Each set of blades slides in a channel on the housing. This allows the blades not currently in contact with the belt to be replaced. The second of the Gordon patents discloses a conveyor belt apron assembly employing "U" shaped brackets. Each bracket being individually biased toward the conveyor belt and each bracket holding a scraper. The tension of this bracket assembly is adjusted by a wedge extending into the side walls of the bracket. The third Gordon patent discloses a plurality of elastomer blades mounted on a shaft. All or some of the blades having a resilient resin torsion member biasing each blade toward the conveyor belt.
All the above patents to one degree or another lack features desirous in a conveyor belt cleaning system. Desirable features include ease of adjustment, compactness of design, shock absorbency, and ease of installation. Known devices use cumbersome and unreliable external torsion spring systems that detract from efficiency.